During the transmission of signals across a neuromuscular junction, which of the following happens last?
acetylcholine binds to a receptor protein on the motor end plate.
sodium and potassium ion gates in the motor end plate open.
synaptic vesicles release acetylcholine molecules.
synaptic vesicles move toward the axon terminals.

Sodium and potassium ion gates in the motor end plate open.

when axon comes close to motor end plate to form neuromuscular junction, synaptic vesicles move toward the axon terminal. these vesicles fuse with the cell membrane of exon terminal and causes release of acetylcholine molecules into synaptic cleft. acetylcholine binds to nicotinic receptors which are concentrated at motor end plate membrane. due to binding of acetylcholine, it causes the receptors to open up and also allow sodium and potassium channels to open up, causing sodium and potassium to enter the motor cells. 

It would be the equator